Description:
A vulnerability reported in CGI applications that run on Apache HTTPD. A remote user can redirect the target CGI application requests to an arbitrary web proxy in certain cases.

On systems where the Apache HTTPD server is configured to proxy HTTP requests and the target CGI application relies on the HTTP_PROXY environment variable in a trusted manner, a remote user can send (or can conduct a man-in-the-middle attack to insert or modify) a specially crafted HTTP "Proxy:" header to cause the target CGI application to proxy HTTP connections to an arbitrary port on an arbitrary server. This can be exploited to set the HTTP_PROXY variable on the target CGI application server and cause CGI application server internal requests to be proxied, in certain cases.

The vulnerability resides in the CGI applications that use the HTTP_PROXY variable.

[Editor's note: This is not an Apache HTTPD vulnerability, per se. Rather, it is a vulnerability in CGI modules or applications that may run on Apache HTTPD or other web server platforms.]

Other CGI application platforms are affected.

The original advisory is available at:

https://httpoxy.org/

Dominic Scheirlinck and Scott Geary of Vend reported this vulnerability. Other researchers have reported aspects of this vulnerability affecting various applications since at least 2001.

Impact:
A remote user that can conduct a man-in-the-middle attack can redirect the target CGI application requests to an arbitrary web proxy in certain cases.